Performance of the Rheumatoid Arthritis Disease Activity Index in the Assessment of Disease Activity in Rheumatoid Arthritis-Findings From the REAL Study.

Background/objective: Although telemedicine use has been under discussion for decades, this topic has gained unprecedented importance during the COVID-19 pandemic. The Rheumatoid Arthritis Disease Activity Index (RADAI) is a user-friendly tool, fully self-administered, to assess rheumatoid arthritis (RA) disease activity. The aim of this study was to compare the performance of RADAI with other disease activity indices, functional status, and inflammatory markers in a large cohort of RA patients.

Methods: We assessed the concurrent validity of RADAI against Clinical Disease Activity Index (CDAI), Disease Activity Score in 28 Joints-C-reactive protein, Disease Activity Score in 28 Joints-erythrocyte sedimentation rate, Simplified Disease Activity Index, and physician assessment of disease activity and the correlation of RADAI with Health Assessment Questionnaire-Disability Index and inflammatory markers at the REAL Study baseline. We also evaluated the correlation of the change in RADAI and the change in CDAI over a 6-month follow-up.

Results: From the 1115 patients included in the REAL Study, 1113 had RADAI scores in the first assessment. At baseline, correlations between RADAI and other disease activity indices were strong, ranging from 0.64 (comparison with physician assessment) to 0.79 (comparison with CDAI). Correlation between the change in RADAI score over the 6 months of follow-up and the change in CDAI score over the same period was moderate/strong for the overall group and within the stratified analyses.

Conclusion: The strong correlation of RADAI with other well-established tools for disease activity measurement reassures its use with RA patients' follow-up, especially in this new era of telemedicine.